On Tuesday, the Colorado Attorney General’s Office joined a multi-state lawsuit to block T-Mobile’s $26.5 billion bid for Sprint.

State attorneys general led by New York and California said the benefits of the merger, such as better networks in rural areas and faster service, cannot be verified. But eliminating a major wireless company, they said, will immediately harm consumers by reducing competition and driving up prices for cellphone service.

Colorado joined eight states and the District of Columbia in filing the lawsuit. T-Mobile and Sprint have about 1.5 million customers in Colorado, according to March 2019 data from the Colorado Public Utilities Commission, about a quarter of the state population.

“To protect Colorado consumers, and the benefits that come from competition, the court should block this merger,” the Colorado Department of Law stated in a news release.

The lawsuit is an unusual step by state officials ahead of a decision by federal antitrust authorities. The Justice Department’s decision is pending. The Republican majority of the Federal Communications Commission supports the deal, though the agency has yet to vote.

T-Mobile and Sprint have argued that they need to bulk up to upgrade to a fast, powerful “5G” mobile network that competes with Verizon and AT&T. The companies are appealing to President Donald Trump’s desire for the U.S. to “win” a global 5G race.

“The $26 billion merger of T-Mobile and Sprint would reduce competition in retail mobile wireless services and the prices that Colorado consumers pay for those services,” the Department of Law stated in the release. “Particularly hard hit would be prepaid customers. Many of these customers come from low-income households and their mobile handsets are their primary-or even only-means of connecting to the internet.”